1. Field of the Invention
The present invention relates to multi-ply bonded metal composites of aluminum cookware articles such as pots and pans and methods for making them.
2. Description of the Related Art
Cookware, such as pots and pans, has been manufactured from aluminum alloy for a considerable time. Aluminum alloy has been a popular metal for the construction of cookware because of its physical properties. Aluminum alloy has a high degree of thermal conductivity, is relatively strong, formable, and is suitable for the application of numerous decorative and functional coatings. The conventional aluminum cookware is usually made from a single layer of aluminum alloy which may be anodized on the outside surface and given a non-stick surface on the inside, cooking surface. Oftentimes such cookware is made from 3003 aluminum alloy or a like aluminum alloy which offers higher strength than purer aluminum such as 1100 aluminum.
It is also well known to manufacture cookware, such as pots and pans, made from composite bonded metal layers of stainless steel with an aluminum core layer or with a copper core layer to improve the thermal conductivity of the composite, as evidenced by U.S. Pat. No. 4,004,892 to Ulam and U.S. Pat. No. 6,267,830 to Groll. It is also known to provide a composite bonded metal construction with a core layer of stainless steel or titanium to provide a heat diffusion layer or “heat dam” to provide a more even heating distribution to the cooking surface as evidenced by U.S. Pat. No. 6,926,971 to Groll.
It is also known to use an “Alclad” layer or layers of pre-bonded aluminum layers in the manufacture of cookware. The Alclad product may consist of a three-layer composite of inner and outer layers of a relatively pure layer of aluminum such as 1100, 1130, 1145 aluminum bonded to a core layer of a stronger aluminum alloy such as 3003, 3004, or 5005 aluminum alloy. The purer aluminum layers offer superior bonding properties for bonding to other dissimilar metal layers such as stainless steel or copper, for example, as disclosed in U.S. Pat. No. 4,246,045 to Ulam. It is also known that Alclad pre-bonded material is produced as a two-layer product consisting of a relatively pure aluminum layer of the 1XXX series, roll-bonded to an aluminum alloy of 3003 or 3004 aluminum alloy for use in cookware, where the aluminum alloy forms the outer layer of the cookware and the pure aluminum is bonded to a layer of stainless steel or copper, for example.